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Review 1: "Distinct age-specific SARS-CoV-2 IgG decay kinetics following natural infection"

Reviewer: Daniel Grupel (Soroka Hospital) | 📗📗📗📗◻️

Published onMar 16, 2022
Review 1: "Distinct age-specific SARS-CoV-2 IgG decay kinetics following natural infection"
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key-enterThis Pub is a Review of
Distinct age-specific SARS-CoV-2 IgG decay kinetics following natural infection
Description

AbstractBackgroundAntibody responses to SARS-CoV-2 can be observed as early as 14 days post-infection, but little is known about the stability of antibody levels over time. Here we evaluate the long-term stability of anti-SARS-CoV-2 IgG antibodies following infection with SARS-CoV-2 in 402 adult donors.MethodsWe performed a multi-center study carried out at Plasma Donor Centers in the city of Heidelberg (Plasmazentrum Heidelberg, Germany) and Munich (Plasmazentrum München, Germany). We present anti-S/N and anti-N IgG antibody levels in prospective serum samples collected up to 403 days post recovery from SARS-CoV-2 infected individuals.ResultsThe cohort includes 402 adult donors (185 female, 217 male; 17 - 68 years of age) where anti-SARS-CoV-2 IgG levels were measured in plasma samples collected between 18- and 403-days post SARS-CoV-2 infection. A linear mixed effects model demonstrated IgG decay rates that decrease over time (χ2=176.8, p<0.00001) and an interaction of time*age χ (χ2=10.0, p<0.005)), with those over 60+ years showing the highest baseline IgG levels and the fastest rate of IgG decay. Baseline viral neutralization assays demonstrated that serum IgG levels correlated with in vitro neutralization capacity in 91% of our cohort.ConclusionLong-term antibody levels and age-specific antibody decay rates suggest the potential need for age-specific vaccine booster guidelines to ensure long term vaccine protection against SARS-CoV-2 infection.

RR:C19 Evidence Scale rating by reviewer:

  • Reliable. The main study claims are generally justified by its methods and data. The results and conclusions are likely to be similar to the hypothetical ideal study. There are some minor caveats or limitations, but they would/do not change the major claims of the study. The study provides sufficient strength of evidence on its own that its main claims should be considered actionable, with some room for future revision.

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Review:

The paper has two distinct parts: the first part uses sequential serological tests to assess IgG long-term decay overtime after natural SARS-CoV-2 infection. The second part attempts to correlate the levels received in the standard serological tests performed to neutralizing antibody (NA) levels, effectively trying to establish the utility of these tests as a correlate of immunity (NA levels have been previously shown to be a good correlate of protection [10.1056/NEJMoa2109072]).

The study finds the highest initial IgG levels in the population above 60 years of age, but also with the fastest decline over time. A good correlation was found between a reactive serological test and a positive neutralization test.

These data align with previous work showing the IgG kinetics after SARS-CoV-2 infection (10.1371/journal.pone.0251159 and 10.1001/jamanetworkopen.2021.4302) but add the significant information of over a year of follow up. This is also the case for the good correlation between serology and neutralization after vaccination (for example, 10.1016/S2213-2600(21)00220-4) And the data and laboratory methods appear robust.

The most important information lacking in the study is the vaccination status of the participants. Although the anti-N test was used as a confirmatory test in some instances, vaccination, which induces antiS response, could affect the anti-N/S response in the population studied.

Furthermore, clinical data regarding pre-existing conditions that could affect antibody production and the recruitment timeframe are also missing.

Despite these limitations, the kinetics of IgG over a relatively long period of time are an important addition to the literature about SARS-CoV2,

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